Method of forming passageways into earth formations penetrated by a well bore



March 8, 1955 J. SUTHERLIN 2,703,619

METHOD OF FORMING PASSAGEWAYS INTO EARTH FORMATIONS PENETRATED BY A WELL BORE Filed May 16, 1952 INVENTOR Jock Suf/rer/in ATTORNEYS METHOD OF FORMING PASSAGEWAYS INTO EARTH FORMATIONS PENETRATED BY A WELL BORE Jack Sutherlin, Wichita Falls, Tex., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware The invention relates to methods of treatment of wells drilled into the earth. It more particularly concerns an improved method for facilitating fluid flow from an earth formation into the bore of a well penetrating the fluid bearing formation and contemplates forming passageways from a well bore into the adjacent earth formation.

In drilling wells for oil, gas, or water, it is always the hope of the driller that the drill will penetrate a stratum from which the desired fluid therein will flow readily into the well. Such hopes are not always realized and the strata penetrated are oftentimes devoid of adequate passageways through which the earth fluids can reach the well. It is the principal object of the invention to provide a method of facilitating fluid flow from a fluid bearing stratum into the bore Of a well drilled thereinto. According to the present invention, a method is provided for forming passageways into fluid bearing strata from a well bore as by subjecting the fluid bearing earth to a high enough hydraulic pressure to fracture and pry apart layers of the earth and introducing a propping agent in the form of solid particles into the resulting passageways so as to hold them open after the hydraulic pressure is released, and thereby facilitating the flow of fluid from the formation. The invention will be readily understood from the following description taken in conjunction with the accompanying drawing illustrating a preferred embodiment of the invention.

In the said drawing, Fig. l is a schematic elevation of a well equipped for carrying out the method and showing the initial stages of the method.

Fig. 2 is a similar view to Fig. 1 and shows the final stages of the method. 1

Referring to the drawing in detail, there is shown a well bore 1 drilled through a fluid stratum 2 which is to be opened according to the method of the invention. The bore above the fluid bearing stratum is provided with the usual casing 3 cemented in place, the lower end 4 of the casing extending to near the top of stratum 2. The casing may be provided with a removable casing head 5 having an opening 6 through which a string of tubing 7 may be hung. The upper end of the tubing is provided with a pipe connection 8 for the admission of fluid to the interior of the tubing. The top of the tubing is provided with a closure in the form of a cap 9 carrying a stufling box 10 through which a wire line 11 may be run carrying a bob 12 on its lower end.

In carrying out the invention, the tubing string is hung in the well, preferably as shown, with the lower end 13 well above the bottom 4 of the casing and the annulus 14 closed near the lower end 13 of the tubing by means of a suitable packer 15. After the tubing is in place, the well is partially filled with a free-flowing hard granular material to form thereof the column 16. The top 17 of the column extends at least several feet above the stratum 2. The particles of the free-flowing hard granular ma terial are more or less equiaxed and, for example, may consist of sand particles, glass beads, ceramic particles, metal particles, and the like. The particle size may range from those just small enough to pass through a Number 6 standard sieve to as small as those just'large enough to be retained on a Number 100 standard sieve. Sands having particles passing through a 12 mesh and remaining on a 40 mesh sieve are used preferably. The particulated material may be introduced into the well in any convenient manner as by means of a dump bailer. Usually the granular material may be introduced by 2,703,619 Patented Mar. 8, 1955 ice is introduced into the tubing through the pipe connection 8 while the wire line 11, stufiing box 10, and cap 9 are in place, and the packer 15 is set. The fluid so-introduced tills the space above the column 16 and penetrates the column of particulated material 16. Hydraulic pressure is also thereby exerted upon the stratum 2 below the end 4 of the casing. This hydraulic pressure is made great enough to exceed the weight of the overburden of earth per unit area thereof and thereby produce cracks or fissures in the adjacent stratum and lifting the overburden. As fracturing or cracking is thus produced and the overburden held up by the lifting action of the pressuring fluid, the free-flowing particulated material of the column 16 above stratum 2 flows into the fractures or cracks which deepen and widen as they fill with the particles while the hydraulic action of the pressuring fluid continues. This action is illustrated in Fig. 2 in which the stratum 2 is shown having a fracture or crack 18 formed thereinextending outwardly from the well bore and filled with particulated material 19 from the column 16 the top of which thereby descends until it reaches the top of the crack. The rate of descent of the top 17 of the column 16 as the particulated material enters the crack shows an abrupt change as the top 17 approaches the top of the crack and can be followed readily by means of the bob 12 on wire line 11 which is allowed to descend with the top of the column 16.

On obtaining such an indication of cessation of flow of particulated material into a stratum, the hydraulic pressure may be released. The particulated material so introduced into the crack remains therein and acts to hold apart the resulting separated earth layers as indicated at 20 and 21. If desired, an additional quantity of particulated material may be introduced into the well and the pressuring operation repeated using the bob 12 and line 11 to ascertain, as described, whether or not the column of particulated material so introduced descends in the casing and thus enters the stratum adjacent to the column.

The following example is illustrative of the practice of the invention.

Example A well having a total depth of 785 feet drilled into 13 feet of Pennsylvania pay sand and having a 7 inch casing extending to a depth of 772 feet produced 23 API gravity oil at the rate of 3 barrels per day before treatment. The well was shut down and then treated as follows. Into this well was dumped 42 gallons (600 pounds) of Ottawa sand and after allowing 15 hours for the sand to settle a measuring line and bob was run into the well to locate the top of the resulting sand column which was thereby found to be at a depth of 763.5 feet. There was feet of oil standing in the well. A retainer was run into the well on 2-inch tubing and the retainer set at a depth of 753 feet. 2 barrels of. 23 API gravity oil were pumped into the well at the rate of 20 G. P. M., thereby producing a pressure at the head of the well of 1000 p. s. i. 2 minutes later, the pressure had declined to 600 p. s. i. while the pumping rate was increased to 60 G. P. M. The injection of oil was then halted and the top of the sand column again located by the wire line and bob. The top of the sand column was thereby found to have descended 11 feet to a depth of 771 feet. The oil injection was then resumed at the rate of 100 G. P. M. causing the injection pressure to reach 1000 p. s. i. which was maintained for 5 minutes. The injection was then halted and the top of the sand column was found to have descended 2.5 feet lower to a depth of 773.5 feet. An additional injection of oil, at the same rate, did not lower the top of the sand column. Three weeks after the foregoing treatment, the well was producing at the rate of 15 barrels of oil per day compared to the rate of 3 barrels per day before the treatment.

Although the practice of the invention has been illustrated using crude oil and sand to produce the earth fracturing and the propping action, respectively, it is to be understood that other hard particulated materials and fluids may be used and in various amounts. For eX- ample, from 300 to 5000 pounds or more of the particulated solid material may be used and other oils or even water may be used for the pressuring fluid.

I claim:

In a method of treating an earth formation penetrated by the bore of a deep well so as to facilitate fluid flow from the formation into the well having the usual casing therein, the steps which consist in filling the bore with a free-flowing particulated hard solid material in amount sufiicient to form a column extending from the bottom of the Well to a level above the bottom of the casing; introducing into the well to contact the column of particulated material therein a liquid under a pressure sufficient 15 2,596,843

References Cited in the file of this patent UNITED STATES PATENTS 2,379,516 Garrison July 3, 1945 2,452,654 Hayes et al. Nov. 2, 1948 Farris May 13, 1952 

